Get captions working on Facebooks ads

If you’ve tried uploading an SRT file to a video on Facebook, you may encounter an error like this:

The captions file you selected is in a format that we don’t support.

What’s wrong? You cry, not that you’re using the standard format for SRT files. It could be that Facebook is throwing an unnecessary hissy fit because you’re using zero-indexing in the blocks, but more likely to be something even simpler: the filename.

Facebook insists that the files are named filename.en_GB.srt, or whatever language combination you are using (for example, filename.en_US.srt. If you don’t include the “.en_GB” bit, Facebook will reject the file, even though it’s a valid SRT file.